Most experimental investigations of left ventricular hypertrophy use animal models in which obstruction to left ventricular outflow is created after birth. While these models do produce left ventricular hypertrophy, they do not reflect the dynamic, compensatory changes that occur prior to birth. We have developed a model of creating left ventricular hypertrophy in utero. The majority of animals (58%) came to term and can be used for chronic investigations of ventricular hypertrophy.